React 19 effects sync execution issues

[Serchinastico]

👋 Hi, while trying to update ink-ui and ink-testing-library to use the latest Ink v6 version, I noticed an issue with the timing useEffect hooks are executed.

While updating to React 19, the reconciler.updateComponent() call was replaced by reconciler.updateComponentSync() and reconciler.flushSyncWork() (changes). I'm no React expert, but I think this has to do with how React 19 now calls useEffect synchronously under certain circumstances (ref).

To keep it short: this change in the timing of hook execution causes an unnoticeable flicker in Ink's output when writing to stderr (which renders non-updated output, in some cases an empty string). It only happens when in debug mode, and it causes some tests in ink-testing-library to fail.

My intuition tells me this would be easily fixable by just re-rendering the tree rather than reusing the last output, but I need to run some tests and make sure that doesn't break anything else.

I'll be opening a PR soon to fix this.

[SandyTao520]

Hi, can you try if #723 fixes the issue?

[Serchinastico]

Hi, can you try if #723 fixes the issue?

Hi! I just tried but unfortunately it didn't solve the issue.